Enable python3.12 and test for all supported versions

[tmillenaar]

While python 3.13.0 is also released as stable, that is not yet supported by sep so we cannot use that python version yet. Python 3.12 worked without any modifications to the code.

I also specified 3.10, 3.11 and 3.12 for testing.
Now you can still just run PYTHONPATH=. hatch run test:pytest, that will test all 3 python version in sequence.
You can now also run with a specific python version like so: PYTHONPATH=. hatch run test.py3.12:pytest

This combines well with the other PR I made (#83) since that one speeds up the runtime of the tests.

[HannoSpreeuw]

Hang on.....I am about to add code that will make it possible to remove both sep and dask as dependencies, but requires Python 3.11, i.e. I cannot get it to work on Python 3.12 yet.

[tmillenaar]

Ah, in that case you can close this MR. Getting rid of the sep and dask dependencies would be quite nice though, I'm all in favor :)
Also, regarding the testing of all versions I added here, that is convenient for local testing but I see now that you have a build step for 3.10 and 3.11 so in that way you already test mutliple versions. That makes my addition a bit redundant